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Rapid optical detection of enterococci in surface water possible

A rapid method for enterococci detection in surface water has been developed which could contribute to more efficient monitoring of microbial water quality. Researchers from KWR, microLAN, Vitens and Het Waterlaboratorium, working within the TKI Water Technology programme, have adapted an existing E. coli detection method, BACTcontrol, which works on the basis of fluorescence. Because the method is still subject to interference from the water matrix, particularly at low (<10 kve) concentrations of enterococci, the results are not solid enough for its immediate, reliable application in practice. This will require further research into the effects of the water matrix and how they might be dealt with. Only subsequently will it be possible to validate the method for online use for drinking water and surface water.

Testing of water microbial safety more rapidly

Contamination with faecal microorganisms is the principal water-related health threat worldwide. This is why the main microbial (legal) parameters for the monitoring of drinking and bathing water quality are Escherichia coli (E. coli) and enterococci, two species of microorganisms that occur in large amounts in faeces. Regulations today require that drinking and bathing water be analysed for the presence of E. coli and enterococci using culture methods. These methods however take one or two days to produce a result. Drinking water companies need faster methods to detect faecal contamination. This will allow them, for instance, to more rapidly detect contaminations that can occur because of pipe fractures or of work on the network, or to put network sections back into operation following work activities. Moreover, fast detection methods could be used to monitor the effectiveness of management measures in the event of contamination incidents, and to determine more rapidly whether surface and bathing water is safe for recreation.

Rapid E. coli method adapted for enterococci

Rapid detection methods are already available for E.coli but not for enterococci. It would make little sense to apply a rapid method for E. coli on its own: no time would be saved. This is why a rapid detection method for enterococci is the objective of this TKI-project. Following a literature review, researchers chose to adapt the rapid E. coli detection system used in microLAN’s BACTcontrol. This method works on the basis of fluorescence: practically all E. coli contain the ß-D-glucuronidase enzyme, which is what the method detects. For E. coli  this method is automatic, sensitive and reliable, and now produces a result in 2.5 to 4 hours. A new version, which only takes 1 to 2 hours to produce a result, will soon be available on the market. The researchers adapted the method’s current version for the detection of enterococci, which contain the ß-D-glucosidase enzyme, and then compared it with existing culture methods in three labs. The adapted method delivers reproducible results when applied to surface water samples and to drinking water, to which the diluted ß-D-glucosidase enzyme has been added. If, after a possible follow-up project, the cause of the interference of the water matrix is identified and resolved, the BACTcontrol will be tested on-site in practice for the online detection of enterococci.